This lens cap is for optical instrument (eg. binoculars, telescopes and spotting scopes) and accessories (eg. eyepieces, Barlow lenses).
Internal Diameter: 55mm (Note: the size is measured as internal diameter of the cap, which is equivalent to the external diameter of the lens including the lens housing).
Depth: 11mm
Material: Rubber.
Note: This listing is for ONE lens cap as described above (not for a pair). This cap is made of rubber material which is flexbile. For this feature, the cap can normally accommodate lenses with slightly bigger diameters. For example, this cap can cover lenses with external diameter around 54.5-56mm.

Note: The size of the lens cap is measured as Internal Diameter of the cap, which is equivalent to the external diameter of the lens including lens housing, as shown in the picture below:
